you can write 10power of -15 as : 10E-15

2^4 as 2E4

Also Please refer the following links:

http://physics.gac.edu/~huber/classes/ph58/pspice.htm

http://home.olemiss.edu/~atef/engr360/tutorial/qgspice.html

Thank you! But it has still a problem. To be more precise, I want to write a complicated expression. It goes like:

IF ( (V(%IN1)-V(%IN3)) >= 0 , (17+95*(V(%IN1)-V(%IN3))-90*abs((V(%IN1)-V(%IN3))-0.005)-80*abs((V(%IN1)-V(%IN3))-0.01)+{-300*abs((V(%IN1)-V(%IN3))-0.015)-200*abs((V(%IN1)-V(%IN3))-0.02)}+{-200*abs((V(%IN1)-V(%IN3))-0.025)-75*abs((V(%IN1)-V(%IN3))-0.03))*(1e-12)}*{sin(2*p*(5*(V(%IN1)-V(%IN3))+19.95)*(V(%IN2))+4.7-60*(V(%IN1)-V(%IN3)))}    ,      (-17+95*(V(%IN1)-V(%IN3))+90*abs((V(%IN1)-V(%IN3))+0.005)+80*abs((V(%IN1)-V(%IN3))+0.01)+{+300*abs((V(%IN1)-V(%IN3))+0.015)+200*abs((V(%IN1)-V(%IN3))+0.02)}+{+200*abs((V(%IN1)-V(%IN3))+0.025)+75*abs((V(%IN1)-V(%IN3))+0.03))*(1e-12)}*{sin(2*p*(5*(V(%IN1)-V(%IN3))+19.95)*(V(%IN2))+4.7-60*(V(%IN1)-V(%IN3)))} )

In this case, when I multiply 3 lines with 10e-12 and simulate, the simulation generates an error:

"ERROR(ORPSIM-16318): Missing or invalid expression"